The invention generally relates to air bags and more particularly to air bags that are required to maintain an effective internal pressure for seconds (rather than milliseconds, which is typical of conventional air bags). The invention is also related to the method of construction of these air bags. One such air bag is a rollover, curtain air bag.
The prior art is replete with air bags designed to protect the driver and the front passenger from frontal crashes. There is also a class of air bags that protect vehicle occupants when the vehicle is involved in a side impact or crash. Typically, these side air bags are located within the door or the outboard side of the seat and, when inflated, provide a barrier between the occupant and the adjacent side of the vehicle. One of the side impact types of air bags is also referred to as a curtain air bag. This type of air bag is located adjacent to the roof rail of the vehicle and, when inflated, moves downwardly along the interior surface of the vehicle side or side structure. As is known in the art, the duration of a crash event involving a frontal, side or rear crash is relatively instantaneous. Consequently, the above types of air bags are designed to be inflated and then deflate within about 100 milliseconds.
The types of material used in the above air bags are somewhat varied. The typical driver side inflator will use woven panels of material that are coated or partially coated and, most often, the rear panel includes vent openings, to accelerate the deflation of the air bag. The larger, frontal passenger side air bags, and to some extent side impact air bags, are constructed utilizing uncoated fabric; of course, the utilization of the more expensive, coated fabrics can be substituted.
A variant of the side curtain air bag (which typically spans two or more support pillars of the vehicle) has been proposed. As mentioned above, the typical side curtain air bag deflates relatively quickly, however, the use of a single air bag, which covers the pillars and the glass windows, has been proposed for use as a rollover air bag to protect the occupant""s head and neck. It is known from many types of rollover tests that the rolling over of a vehicle may take many seconds to complete. As such, it is desirable to provide an air bag in which inflation gas is trapped therein for a relatively long period of time and at an acceptable pressure, which yields in essence a semi-permanent pillow or cushion to protect the occupant""s head and neck.
Those skilled in the art have appreciated that one of the main sources of air bag leakage, particularly when main panels are coated, results from the many thousands of needle and thread holes created while sewing and forming outer seams of an air bag. The sewn seam can be totally eliminated by constructing a virtually or completely interwoven air bag, which is then coated on both sides to reduce to porosity of the bag. However, such construction typically requires the use of expensive and relatively slow weaving looms, such as a Jacquard head with a standard loom, and such construction is not part of the present invention.
It is an object of the present invention to provide an air bag that can be used in a rollover crash event. A further object of the present invention is to provide such a rollover air bag that is simple to construct and one that does not require expensive and exotic machinery to produce.
A further object of the present invention is to provide a rollover air bag formed by sewing two separate panels of coated material together or, alternatively, a rollover air bag formed by folding in half a single main panel of material and sewing the resulting first and second opposing halves or panels of this large main panel together, the seams constructed to retain gas for long periods of time.
Reference is made to FIG. 1, which illustrates a prior art construction of an air bag 20 formed of two facing panels of material 22 and 24. Each of the panels may include low-porosity coating, such as 26, typically formed of silicone or urethane. The panels 22 and 24, including their coating, are connected by one or more sewn seams 28. As the interior of the air bag is inflated, the panels move apart, stressing the seam. As can be appreciated, inflation gas leaks out of the air bag between the panels 22 and 24 (see arrow 30) as well as through the needle holes. The airflow through the needle holes is shown by arrows 32.
European patent EP 962363 refers to a prior art solution to gas leakage shown in FIG. 2 in which a sealant 34 is applied about the exterior of seam 28, sealing the thread and needle holes while still permitting the outflow of gas between the tensioned panels 22 and 24. The panels 22 and 24 of FIG. 2 are not shown with a non-permeable coating 26. Another prior art solution to gas migration inserts an RTV sealant 36 between the two panels 22 and 24 and then sews the panels together by a dual row of stitches (seams) 28 and 28xe2x80x2, which is reproduced in FIG. 3. U.S. Pat. No. 5,687,986 shows a seam with increased strength in which a strip of material 38 is bent about the joined edges of the two panels 22 and 24 and sewn together; the construction is shown in FIG. 4. The use of silicone sealants interior to the panels, exterior of the panels, or some combination thereof is messy, expensive and slows the throughput of the production processes. A solution such as shown in FIG. 4 complicates the sewing process as the strip of material 38 must be positioned about the edges of both panels and sewn to the panels.
As can be appreciated, as the length of the air bag (as with a long curtain air bag) increases, the length of the sewn seam or seams, utilized to secure the panels 22 and 24 (whether coated or uncoated), increases, thereby increasing the opportunity for gas to flow through this ever increasing coupling.
Accordingly the invention comprises: a safety apparatus including a rollover air bag to protect an occupant not only during the rolling-over of the vehicle but also in side impact crashes, the air bag comprises: first and second panels of woven material that has been coated on at least one side thereof to reduce the porosity of material to substantially zero. The panels are sewn together along a first sewn seam to define an inflatable portion of the air bag. The air bag includes seam sealing means for sealing the first sewn seam so that the internal pressure of the air bag at about five (5) seconds after the air bag is initially inflated is about 20 Kpa (about 0.5 psi) or higher depending on the geometry of the cushion. In one embodiment a pressure adhesive tape is employed and in another a heat sensitive tape can be applied.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.